Heretofore, a display device and an input device have been fabricated as different devices, and the input device, which is constituted by, e.g. buttons, has been usually disposed in the vicinity of the display device (for example, see FIG. 15). FIG. 15 is an illustrative view showing a conventional example where a display device and an input device are independently disposed. In the conventional example shown in FIG. 15, the display device 70, which includes a liquid crystal panel having a liquid crystal 83 sandwiched between two transparent substrates 81 and 82, and an input device 71, which includes a transparent substrate 91 having electrodes for sensors 89 disposed thereon, are independently disposed as different devices.
When the display device and the input device are disposed as different devices, there is a problem that a large area is required for a space for incorporating the display device and the input device between both devices. When the display device and the input device are disposed side by side, there are a problem that it is impossible to dispose the display device and the input device in succession since it is difficult to bring a display portion (portion where electrodes for liquid crystal display 85 are disposed) and an input portion (portion where the electrodes for sensors 89 are disposed) close to each other, and a problem that it is necessary to manufacture the two devices independently.
As the method for reducing the required area, there is a method for disposing a transparent input device on a display device (for example, see FIG. 16). FIG. 16 is an illustrative view showing another conventional example where the display device and the input device are independently disposed. In the conventional example shown in FIG. 16, the input device 71, which includes a transparent substrate 91 having electrodes for sensors 89 disposed thereon, is disposed, in an overlapping fashion, on the display device 70 (a viewer's side) which includes a liquid crystal panel having a liquid crystal 83 sandwiched between two transparent substrates 81 and 82.
As the transparent input device, a resistance film type, a surface capacitive type, a projection capacitive type, a surface acoustic wave type, an optical type and the like have been proposed. However, even in the case of adopting such a method for disposing a transparent input device on a display device, it is necessary to independently dispose the input device, which causes a problem in that the cost is high.
In order to solve the problem caused by disposing independently the display device and the input device, a method for integrating the display device and the input device has been proposed.
Patent Document 1 discloses a method for fabricating a display portion and an input portion on a single substrate. Patent Document 1 also discloses a liquid crystal display device and a resistance film type touch panel as an example.
Further, Patent Document 2 discloses a method for simultaneously fabricating touch type sensors in a process for fabricating a TFT for a TFT (Thin Film Transistor) liquid crystal display.
Further, Patent Document 3 discloses a method for realizing a liquid crystal display device with a touch function by disposing photosensors for detecting light, on a peripheral portion of a liquid crystal display device (peripheral portion close to a display portion corresponding to touch keys).
Further, Patent Document 4 disclose a method for integrating a display device and an input device by forming a pixel circuit in a display portion and a sensing circuit for detecting capacitance in a sensing area. This document discloses a method wherein a change in the thickness of a liquid crystal layer caused by a load given by a finger is detected as a change in capacitance by the sensing circuit.